Global calorie availability could be increased by as much as 70 per cent — feeding an additional 4 billion people — by shifting cropland use to produce food for humans rather than livestock feed and biofuels, according to new research.

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Such a shift could free up calories roughly equivalent to the yield increases achieved for maize, wheat and rice between 1965 and 2009, researchers say in the study, published in Environmental Research Letters this month (1 August).

"When talking about the future of food security, people often suggest that we grow our way out of the problem: that if we just keep producing more corn and soybeans we will be able to feed the world.

Our study provides an alternative point of view," Emily Cassidy, lead author of the study and environmental scientist at the University of Minnesota, United States, tells SciDev.Net.

Researchers looked at the 41 crops that provide more than 90 per cent of world's calories. They analysed where the crops are grown, the overall production and also how the crops are used: for direct human consumption, animal feed or biofuels.

"Globally, 36 per cent of all calories are fed to animals. We found that decreasing grain-fed meat consumption by 50 per cent would be enough additional calories for two more billion people," says Cassidy.

Reducing meat consumption, or shifting it away from beef to poultry and pork, has the potential to feed more people per hectare of cropland because beef is not energy efficient, Cassidy adds.

"When we feed 100 calories of average corn and soy to beef cattle we get only three per cent of these calories back, while the efficiency is better for pork and chickens," she says.

Researchers also looked at crop allocation in terms of proteins.

"Half of the protein that we produce with crops actually goes to animals for feed. We could have the right amount of protein and amino acids if we were to directly consume crops," says Cassidy. "We are actually losing a lot of protein in the plant-animal conversion process."

Yet, the authors recognise that the recent global trends are towards more meat consumption and biofuel production.

"Meat is part of the human culture and it's important for food security in many parts of the world, but when we increase crop yields in affluent nations we are just feeding animals and this is not turning into much food for human consumption," says Cassidy.